1. Field of the Invention
This invention relates to power tongs and more particularly to a device for rotation of elongated goods and a reversing pin therefor.
2. Description of the Prior Art
Before this patent application was filed, applicant caused a patentabiltiy search to be made in the U.S. Patent and Trademark Office. The following patents are reported:
MASON: U.S. Pat. No. 3,086,413 PA0 CATLAND: U.S. Pat. No. 3,261,241 PA0 KELLEY: U.S. Pat. No. 3,371,562, PA0 DICKMANN: U.S. Pat. No. 3,540,326, PA0 DICKMANN: U.S. Pat. No. 3,548,692, PA0 WILMS: U.S. Pat. No. 3,706,243, PA0 WILMS: U.S. Pat. No. 3,793,913, PA0 BUFKIN: U.S. Pat. No. 3,847,040, PA0 DREYFUSS ET AL: U.S. Pat. No. 3,875,826, PA0 ECKEL: U.S. Pat. No. 4,084,453, PA0 ECKEL: U.S. Pat. No. 4,089,240, PA0 CARSTENSEN: U.S. Pat. No. 4,215,602, PA0 ECKEL: U.S. Pat. No. 4,290,304.
MASON U.S. Pat. No. 3,086,413 and DREYFUSS ET AL U.S. Pat. No. 3,875,826 appear to show beveled pins. However, as applicant understands these devices, they are for different purposes than his invention.
Applicant does not consider the other patents particularly pertinent to this invention, but is bringing them to the attention of the Examiner because they were reported to the applicant by an experienced patent searcher. Therefore, the applicant believes they would be of interest to the Examiner.
Power tongs for wells and more particularly oil wells are well-known and take different forms. Basically, the tongs include an annular housing plate. A torque arm is attached to the housing so that torque may be applied to the goods to be rotated. The goods may be either a casing, which has a relatively large diameter (7 or 8 inches), drill pipe, production or education tubing, or sucker rods.
A ring gear is mounted within the housing plate for rotation. The outside periphery of the ring has teeth driven either by a series of rotating gears or by a chain. A cage plate is coaxial with the ring gear and also with the annular housing plate. The cage plate may rotate relative to each. At least two heads are moveably mounted on the cage plates. These heads include jaws or teeth which engage the goods. The jaws are next to the axis of rotation. A cam follower is on the distal end of each head. The follower engages a cam on the inner face of the ring gear. The cam follower is often in the form of a roller. The cams on the inner face of the ring gear have neutral positions. This is where the heads are fully withdrawn from the goods so that the goods are released from the tongs.
Most power tongs have a means to open the housing plate, ring gear, and cage plates so that the tongs can be moved radially over the goods.
One particular type includes a slot in the annular housing plate, ring gear and cage plates. Therefore, if the slots in each of the elements were aligned, or matched, then the sucker rods or other goods can be moved through the slot to the axis of the power tongs.
Rotation in one direction will move the ring gear relative to the cage plates so that the cams push the heads for the goods to be rotated. Therefore, the ring gear must be free to rotate relative to the cage plates in the direction which the goods are to be rotated. However, to release the goods, the drive means for the ring gear is reversed so that the cam followers are brought back to the neutral or withdrawn position on the cams. This position occurs at the point the slots in the ring gears and cage plates will match. To prevent opposite rotation, it is necessary to lock or stop relative rotation of the ring gear to the cage plate at this matched position. The prior art accomplishes this by placing a pin through a hole in the cage plate that engages a lug upon the ring gear to stop relative rotation between these two elements in this position.
To change the sense or direction of rotation which the goods would be rotated, it was necessary to remove this pin and set it into another hole so that rotation would be allowed in the other direction, but would stop upon the reversal.